In recent years, much of the indium in Japan has been used in transparent conducting films in the form of indium-tin oxide (hereinafter, ITO) or indium-zinc oxide (hereinafter, IZO), and this constitutes approximately 70% of the entire market for indium (when recycled indium is included, this becomes almost 80%).
On the other hand, the flat panel display (hereinafter, FPD) industry, which uses transparent conducting films, has recently experienced a dramatic increase in the demand for thin-type and large-type televisions, in addition to the demand for liquid crystal displays for personal computers. The tightening of lead restrictions by the EU is expected to increase the need for indium due to the increased demand for leadless solder that is made from low melting-point alloys that include indium.
Market trends point toward a rise in the price of indium, and it is foreseeable that the situation will become a “competition” to secure raw indium.
On this backdrop, there are increasing opportunities to recycle indium, and one might say that the recycling of indium is more than just a simple environmental technology, but rather a “material recovery” technology that has important economic value.
Some conventional examples of the technology for recycling indium include eluting an ITO target, etc. with acid and then isolating and recovering the indium by removing impurity metal ions through a sulfide method (for example, see Patent Document 1) or a hydroxide method (for example, see Patent Document 2), or with a chelate resin (for example, see Patent Document 3), or through solvent extraction (for example, see Patent Document 4).
Indium that has been isolated and recovered by an above method is then refined by an electric field refining method (for example, see Patent Document 5) or the like.
Patent Document 1: JP 2000-169991A
Patent Document 2: JP 2002-69684A
Patent Document 3: JP 2002-308622A
Patent Document 4: JP 2000-212658A
Patent Document 5: JP H6-248370A